Mutations in AEC syndrome skin reveal a role for p63 in basement membrane adhesion, skin barrier integrity and hair follicle biology.

BACKGROUND: AEC (ankyloblepharon-ectodermal defects-clefting) syndrome is an autosomal dominant ectodermal dysplasia disorder caused by mutations in the transcription factor p63. Clinically, the skin is dry and often fragile; other features can include partial eyelid fusion (ankyloblepharon), hypodontia, orofacial clefting, sparse hair or alopecia, and nail dystrophy. OBJECTIVES: To investigate how p63 gene mutations affect gene and protein expression in AEC syndrome skin. METHODS: We performed microarray analysis on samples of intact and eroded AEC syndrome skin compared with control skin. Changes were verified by quantitative real-time reverse transcription-polymerase chain reaction and, for basal keratinocyte-associated genes, by immunohistochemistry and analysis of microdissected skin. RESULTS: We identified significant upregulation of six genes and downregulation of 69 genes in AEC syndrome skin, with the main changes in genes implicated in epidermal adhesion, skin barrier formation and hair follicle biology. There was reduced expression of genes encoding the basement membrane proteins FRAS1 and collagen VII, as well as the skin barrier-associated small proline-rich proteins 1A and 4, late cornified envelope protein 5A, hornerin, and lipid transporters including ALOX15B. Reduced expression of the hair-associated keratins 25, 27, 31, 33B, 34, 35, 81 and 85 was also noted. We also confirmed similar alterations in gene expression for 26 of the 75 genes in eroded AEC scalp skin. CONCLUSIONS: This study identifies specific changes in skin structural biology and signalling pathways that result from mutant p63 and provides new molecular insight into the AEC syndrome phenotype.

Molecular basis of EEC (ectrodactyly, ectodermal dysplasia, clefting) syndrome: five new mutations in the DNA-binding domain of the TP63 gene and genotype-phenotype correlation.

Summary EEC (ectrodactyly, ectodermal dysplasia, clefting; OMIM 604292) syndrome is an autosomal dominant developmental disorder. Characteristic clinical features comprise abnormalities in several ectodermal structures including skin, hair, teeth, nails and sweat glands as well as orofacial clefting and limb defects. Pathogenic mutations in the TP63 transcription factor have been identified as the molecular basis of EEC syndrome and to date 34 mutations have been reported. The majority of mutations involve heterozygous missense mutations in the DNA-binding domain of TP63, a region critical for direct interactions with DNA target sequences. In this report, we present an overview of EEC syndrome, discuss the role of TP63 in embryonic development and skin homeostasis, and report five new TP63 gene mutations. We highlight the significant intra- and interfamilial phenotypic variability in affected individuals and outline the emerging paradigm for genotype-phenotype correlation in this inherited ectodermal dysplasia syndrome.

Rapp-Hodgkin and Hay-Wells ectodermal dysplasia syndromes represent a variable spectrum of the same genetic disorder.

BACKGROUND: Rapp-Hodgkin syndrome (RHS) and Hay-Wells [also known as ankyloblepharon-ectodermal defects-cleft lip/palate (AEC)] syndrome have been designated as distinct ectodermal dysplasia syndromes despite both disorders having overlapping clinical features and the same mutated gene, TP63. OBJECTIVES: To search for TP63 mutations in two unrelated cases of RHS and two of AEC syndrome and to review the TP63 mutation database and clinical descriptions of affected individuals, the goal being to refine genotype-phenotype correlation and to determine the clinical/molecular justification for RHS and AEC continuing to exist as separate entities. METHODS: Clinical examination of four affected cases and sequencing of genomic DNA using TP63-specific primers. Literature review of published clinical descriptions of RHS and AEC syndrome cases containing TP63 mutation data. RESULTS: Cases of RHS and AEC show considerable clinical overlap, particularly with regard to hypotrichosis and mid-face hypoplasia, and the clinical feature of ankyloblepharon in AEC is often subtle, transient and a poor distinguishing clinical sign. We identified two new and two recurrent heterozygous mutations in TP63: c.1456insA (p.Leu486fsX52), RHS; c.1537T>G (p.Phe513Val), RHS; c.1787delG (p.Gly596fsX68), AEC; and c.1682G>A (p.Gly561Asp), AEC. Including this study, 42 different mutations in TP63 in RHS and AEC have now been reported, three of which are exactly the same in both syndromes. CONCLUSIONS: Our clinicopathological and molecular findings indicate that there is no justification for the continued use of eponyms in referring to these particular ectodermal dysplasia syndromes. We support the view that the terms 'Hay-Wells' and 'Rapp-Hodgkin' should be abandoned in favour of the all-inclusive diagnosis 'AEC syndrome', notwithstanding the inconsistency or often transient nature of the ankyloblepharon.